Proportional sampling apparatus

ABSTRACT

A PROPORTIONAL SAMPLING APPARATUS FOR SELECTIVELY WITHDRAWING AND PROPORTIONATELY MIXING TWO SEPARATE FLUIDS FOR SAMPLING PURPOSES IS DISCLOSED THEREIN. THE APPARATUS COMPRISES A SUCTION CONDUIT VERTICALLY M,OUNTED ONE ONE END OF A LEVER ARM, THE OTHER END OF THE LEVER ARM BEING COUPLED TO A CRANK WHEEL. A CAM FOLLOWER IS MOUNTED ON THE LEVER ARM ADJACENT A TRIANGULAR SHAPED CAM, ACTING AS THE LEVER ARM FULCRUM. A PAIR OF LAUNDERS EACH CONTAINING ONE OF THE FLUIDS TO BE WITHDRAWN IS MOUNTED BELOW THE SUCTION   CONDUIT, THE ADJACENT WALLS OF EACH LAUNDER BEING POSITIONED BELOW THE LEVEL OF THE SUCTION CONDUIT WHEN IT IS RAISED ABOVE THE LEVEL OF FLUID IN THE LAUNDERS. FLUID WITHDRAWN SEQUENTIALLY THROUGH THE SUCTION CONDUIT IS METERED INTO A MIXING TANK THROUGH A SOLENOID VALVE RESPONSIVELY CONTROLLED BY SWITCH MEANS, AND SWITCH MEANS BEING RESPONSIVE TO THE CRANK WHEEL POSITION.

Filed March 11, 1970 2 Sheets-Sheet 1 om/ om ow, mm

3 3 v mm m o mm 0 A0 W on 3 4 v A INVENTOR. EDWARD J. .,REBES ATTORN EY NOV. 2, 1971 J TREBES 3,616,694

PROPORTIONAL SAMPLING APPARATUS Filed March 11, 1970 2 Sheets-Sheet 2 FIG. 5

INVENTOR. EDWARD J. TREBES Y 1 l I \WQIZZI" 7. ATTORNEY United States Patent O 3,616,694 PROPORTIONAL SAMPLING APPARATUS Edward J. Trebes, Tampa, Fla., assignor to Cities Service Company, New York, N.Y. Filed Mar. 11, 1970, Ser. No. 18,435 Int. Cl. G01n 1/14 US. Cl. 73-423 A 6 Claims ABSTRACT OF THE DISCLOSURE A proportional sampling apparatus for selectively withdrawing and proportionately mixing two separate fluids for sampling purposes is disclosed herein. The apparatus comprises a suction conduit vertically mounted on one end of a lever arm, the other end of the lever arm being coupled to a crank wheel. A cam follower is mounted on the lever arm adjacent a triangular shaped cam, acting as the lever arm fulcrum. A pair of launders each containing one of the fluids to be withdrawn is mounted below the suction conduit, the adjacent walls of each launder being positioned below the level of the suction conduit when it is raised above the level of fluid in the launders. Fluid withdrawn sequentially through the suction conduit is metered into a mixing tank through a solenoid valve responsively controlled by switch means, the switch means being responsive to the crank wheel position.

BACKGROUND OF THE INVENTION This invention relates to an apparatus for sampling and mixing two different fluids. More particularly this invention relates to an apparatus for proportionately withdrawing two samples of fluid from separate sources and mixing them preparatory to subjecting the mixed fluid sample to automatic analysis. Automatic analysis of fluid samples from process streams is presently a commercially significant practice with the test results being in many instances used in the automatic control of the process conditions. Where the automatic test devices are of a type which analyze the process fluid after the fluid has been mixed with a second fluid in a predetermined proportion, the automatic acquisition of a satisfactory test sample mixture suitable for analysis poses a problem. In aquiring such a sample, it is conventional to use a proportioning pump and these types of pumps are generally satisfactory when the ratio of the two fluids to each other is close to unity. However where the volurnetric ratio of the fluids is necessarily large there are no presently satisfactory methods or apparatus for automatically obtaining and proportioning a sample. Additionally, proportioning pumps are very expensive and are prone to malfunction if solids are present in the process fluids. For instance in certain processes such as the wet process for producing phosphoric acid, a certain amount of crystallization occurs at pump inlets and lead to such plugging.

A particular application for such automatic analysis is the wet process production of phosphoric acid by the acidulation of phosphate rock. The hot, saturated wet process phosphoric acid product, prior to analysis by automatic analysis instrumentation must be precisely diluted with water. Apparatus for automatically and precisely accomplishing this objective is the particular subject of my invention.

SUMMARY OF THE INVENTION Accordingly I have invented an apparatus for selectively withdrawing two diflferent fluid samples from separate and adjacent sources. The apparatus comprises means for pumping a fluid, a suction conduit communicatingly connected to the intake of the pumping means, means for in- Patented Nov. 2, 1971 serting the suction conduit into a first medium, withdrawing the conduit from the first fluid medium and inserting the conduit into a second fluid medium for a predeter mined period of time, and means for mixing the withdrawn fluids. Preferably the means for inserting the suction conduit into the first and second fluid medium comprises a lever arm having one end attached to a crank which applies a reciprocating movement to the arm, and the other end supports the suction conduit. A cam follower is attached to the pivot point of the lever arm, and is in sliding contact with a cam fulcrum to elevate the pivot point at the mid-point of the transverse movement of the lever arm. The cam is preferably either shaped as an erect isosceles triangle or semi-circle, whereby the path followed by the suction conduit attached to the lever arm sequentially clips the suction conduit into the first fluid medium, then removes the conduit and dips the suction conduit into the second fluid medium in continuing sequence. A valve actuated in response to the position of the lever arm is controllingly opened for a predetermined amount of time and is communicatingly connected between the pump and the suction conduit.

It is therefore an object of this invention to provide apparatus for selectively and proportionately withdrawing fluid from two separate sources.

Another object of this invention is to provide apparatus for automatically controlling the proportion and quantity of the separately withdrawn fluids.

Other objects and advantages of the apparatus according to this invention will become apparent from the brief description of the drawings and preferred embodiment which follow.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic elevation of the apparatus according to the present invention;

FIG. 2 is an abbreviated schematic showing the apparatus in a position for not withdrawing any fluid;

FIG. 3 is another abbreviated schematic drawing showing the apparatus in position to withdraw fluid from the second of the two sources;

FIG. 4 is a schematic view of the drive mechanism showing the arrangement of mechanical elements of the valve control; and

FIG. 5 is a circuit diagram of the valve control instrumentation.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENT The proportional sampling apparatus of this invention is preferably used to automatically withdraw a predetermined quantity of hot wet process phosphoric acid and to dilute the sample with a predetermined quantity of water prior to subjecting the diluted sample to automatic quantitative analysis. The wet process phosphoric acid is contained in a vessel, more precsely described as a first constant level launder 12, which is defined as a box conduit. The level of the hot acid stream is relatively constant over an appreciable length of time. Adjacent the first launder is a second launder 14 containing, in this instance water, also at a constant level and serving as a source of the water of dilution. The distance between the adjacent walls of each of the launders is small to enable the apparatus to reach each launder in turn as will be hereinafter described.

A lever arm 16 is mounted above the two launders with its principal axis being generally horizontal and parallel to a line drawn between the two launders cross-sectionally. The lever arm may be any structural shape such as a box, a rectangular bar, an angle iron or a pipe, so long as it is rigid enough to support a suction conduit 18 on one of its ends designated herein as the support end 20. The suction conduit is a vertically mounted pipe having an opening 22 at its lower end extending a sufi'icient distance below the support end 20 to adequately clear the sides of the launders. The other end of the suction conduit is connected to a flexible hose 24, the operation of which will be further elaborated on.

Referring back to the lever arm, the end opposite the support end is designated as the drive end 26 and is pivotally connected to a crank 28. The crank 28 is structurally a wheel, having a horizontal axis which is generally perpendicular to the long axis of the lever arm the crank being supported on a drive shaft '30. The drive shaft is connected a constant speed reversible drive means such as a geared electrical motor 32. (In the specific embodiment shown, a wheel is the preferred form of crank drive due to the fact that its inertial characteristics enhance the constant speed design of the motor 32.) Two timer cams, a first timer cam 34 and a second timer cam 35 are also mounted on the drive shaft.

The lever arm has as its fulcrum a triangularly shaped fulcrum cam 38. The fulcrum cam 38 is preferably in the shape of an upright isosceles triangle although it should be understood that other shapes such as a semi-circle may be employed. Mounted on the lever arm adjacent the fulcrum cam is a fulcrum cam follower 40. The fulcrum cam follower is preferably a relatively small wheel rotatably mounted to one side of the lever arm, enabling the arm to clear the fulcrum as the fulcrum cam follower slidingly moves along the upper sides of the fulcrum.

Reversible rotation of the crank by the motor 32 through an angle of 180, and more specifically from 90 to 270 imparts a reciprocal motion to the lever arm along its axis. Such reciprocal motion causes the fulcrum cam follower to slidingly move over the fulcrum cam. Since the fulcrum cam is so mounted in relation to the fulcrum cam follower that the follower is at the apex of the triangle when the crank wheel has positioned the crank end midway in its reciprocal motion, the conduit support end of the lever arm will be at its maximum elevation at which point the suction conduit is midway be tween and above both of the launders. Similarly when the lever arm is at either end of its reciprocal motion the fulcrum cam follower is on one side or the other of the triangular cam fulcrum and the lever arm support end is at its lowest elevation. This latter point occurs at either end of the reciprocal motion of the lever arm when the crank wheel is either at 90 or at 270. The support end of the lever arm is also at the same time being moved reciprocally in the horizontal plane so that the support end is displaced horizontally a length equal to the diameter circumscribed by the lever arm crank end from 90 to 270. As is apparent this displacement must be suflicient to carry the support end the distance between the two launders plus the added distance needed to clear the adjacent launder walls and insert the suction conduit in the launders. As the constant speed reversing motor cycles through the 180 arc the suction conduit will therefore be inserted in first one launder, then removed, and inserted in the other launder and then back to the first launder in continuous sequence.

The suction conduit 18 and flexible hose 24 is connected to a solenoid valve 42. The solenoid valve is controlled by electrical circuitry responsive to the position of the crank and therefore to the location of the suction conduit and for a specific preset period of time. The solenoid valve is in turn connected to a pipe 44 leading to a mixing tank 46. The mixing tank utilizes magnetic mixing, a well known and conventional means for mixing samples, and is sized to eliminate the formation of acid-water cycles passing to the analytical equipment. A mixer outlet pipe 48 leads from the mixing tank to a continuous operation positive displacement pump 50, also of conventional design. The size of the mixing tank is preferably equal in volume to the one minute operating capacity of the pump. A pump outlet pipe 52 is connected to the pump and leads to the analytical equipment not shown for quantitative analysis of the sample.

as control for both the drive motor direction and the solenoid valve through the inter-connecting circuitry. Briefly the first microswitch 58 is a normally closed switch connected to wire 62 and to one side of a first time delay (TD) relay 64. Wire 62 is connected to a source of electrical power, not shown. Time delay relay 64 is a normally open switch connected to wire 62 on one side and on the other side to one field 68 of the drive motor and to a solenoid valve relay 68 which is normally closed. Similarly the second microswitch 60 which is also a normally closed switch activated by the cam 36 is connected on one side to wire 62 as a current source, and on the other side to a second motor time delay (TD) relay 70. The second time delay relay 70 is a normally open relay having a fixed time delay after it is energized and applies cur rent to the second field 72 of the motor :and to the solenoid valve relay for the period of the time delay. The solenoid valve 42 is a normally open valve which is energized at the same time as either of the two motor fields 66- and 72. The valve is therefore closed during the period when the drive motor is energized.

In operation therefore the constant delivery pump is continually operating. However fluid passes into the pipe system only during the time that the normally open solenoid valve is not energized. Thus the drive motor is continually cycling through an angle of driving in one direction until the timer cam 34 actuates microswitch 58 to open the circuit to the first time delay relay 64. This point is at the end of one directional cycle and the suction conduit is therefore inserted into the first launder 12 holding the hot acid. The time delay relay 14 for the preset time period keeps the circuit to the motor and to the solenoid valve relay open and therefore not energized. During this time period the solenoid valve is open and fluid can be drawn from the hot acid launder. When the delay time period has terminated, the motor is energized and driven in the opposite direction, until the second cam 36 actuates the second microswitch 60, at which time the second TD relay 70 opens the circuit stopping the motor and opening the solenoid valve again. This point corresponds to the position at which the suction conduit is inserted into the second launder containing the water. The solenoid valve remains open and the motor remains unenergized for the length of time the second time delay relay 70 1s preset to.

In operating the proportional sampling apparatus for the sampling of hot wet process phosphoric acid, a ratio of 1 volume of acid to three volumes of water of dilution is frequently employed. Accordingly the two time delay relays are preset to give the second time delay relay 70 a delay of 3 times that of the first time delay relay 64. Where the positive displacement pump has a 1 gal. per hour capacity at 88 strokes per minute and the mixing tank a volume of about 70 milliliters, the sampling apparatus was found to have a proportioning error of between plus or minus 0.8%, or less than one percent. An added advantage of the apparatus of this invention is its selfcleaning characteristic. As previously mentioned hot wet process acid tends to crystallize somewhat upon cooling and this would normally lead to plugging of the intake or suction pipe leading. from the hot acid launder. In the present apparatus the sequential insertion of the suction conduit into the water launder serves to prevent such crystallization from accumulating and continually dissolves and washes any solid from the suction conduit.

While the apparatus of this invention has been described with respect to the preferred embodiment thereof, it should be apparent that various modifications can be made without departing from either the scope or spirit of this invention. For instance a reciprocating motion can be applied to the lever arm by a linear actuator such as a solenoid or a hydraulic piston.

Therefore I claim:

1. Apparatus for selectively drawing a number of fluid samples from different sources comprising,

means for pumping fluid,

a suction conduit communicatingly connected to an intake of said pumping means,

a rotatably mounted drive wheel,

a lever arm pivotably and eccentrically connected to said drive wheel at one end, and to said suction conduit at the other end,

a cam follower mounted on said lever arm intermediate of said lever arm ends, and

camming means positioned adjacent said lever arm cam follower, said camming means acting as a fulcrum for said lever arm whereby said suction conduit is sequentially inserted into a first fluid medium for a specific predetermined period of time, then withdrawn from the first fluid medium, and inserted into a second fluid medium for a specific period of time.

2. The apparatus of claim 1 wherein said pumping means is a positive displacement pump.

3. The apparatus of claim 1 wherein said camming means is an upright triangularly shaped cam, said lever arm and cam follower are so positioned with respect to each other so that said cam follower is of the apex of said cam when said pivotally mounted end of said lever arm drive wheel eccentric is at 180 angular displacement from a vertical line drawn through the drive wheel axis.

4. The apparatus of claim 3 wherein a solenoid valve is communicatingly mounted in said suction conduit, said solenoid valve being responsively connected to means for selectively opening said valve for selected predetermined intervals when said suction conduit is inserted successively in said first and said second fluid mediums.

5. The apparatus of claim 1 wherein a solenoid valve is communicatingly mounted in said suction conduit, said solenoid valve being responsively connected to a means for selectively opening said valve for selected predetermined intervals when said suction conduit is inserted successively in said first and said second fluid medium.

-6. The apparatus of claim 5 which additionally comprises a means for mixing fluid communicatingly connected to the upstream side of said pumping means.

References Cited UNITED STATES PATENTS 3,449,959 6/1969 Grimshaw 73423 A 3,484,170 12/1969 Smythe 73423 A 2,742,788 4/1956 Henton 73-421 B S. CLEMENT SWISHER, Primary Examiner UJS. Cl. X.R. 23253 

